Grain growers are encouraged to monitor for mouse activity this spring as there remains potential for crop damage in some areas.
The GRDC-supported National Mouse Management Working Group is urging growers not to become complacent and to continue monitoring for mice on a paddock-by-paddock basis, looking for the presence of mice, mice holes and chewing damage.
The working group chair, Ian Hastings, says growers may need to be ready to apply bait if higher-than-normal activity is identified.
Although mouse activity in autumn was generally low in New South Wales, Tasmania and Queensland, areas in other states were reporting higher-than-usual levels of activity.
In Western Australia, high activity levels were reported:
- near York, Shackleton and Cadoux;
- in the Ravensthorpe and Esperance region including Cascade and Beaumont;
- in the northern agricultural zone near Binnu, Yuna, Eradu, Tenindewa, Mullewa and Mingenew; and
- at Wongan Hills.
In Victoria, mouse activity in autumn was high in parts of the Wimmera, particularly east of Nhill and near Rupanyup, as well as at the western end of the Millewa region and at Carwarp, south of Mildura.
In South Australia, high mouse activity was reported in the coastal areas of the northern Adelaide Plains, on Eyre Peninsula near Wudinna and, to a lesser extent, between Cleve and Tumby Bay and on the west coast near Wirrulla.
Although activity was generally low on SA’s Yorke Peninsula, isolated hotspots were reported along the coast in the Port Victoria region.
For the past two years, SA grain grower Ben Wundersitz has spent $80,000 to $100,000 annually on bait to control mice on the 5600 hectares he crops on SA’s Yorke Peninsula.
While Mr Wundersitz’s home property near Maitland totals 728ha, he manages a further 4872ha under share-farming and leasing arrangements in blocks located from Port Victoria in the west to Ardrossan in the east.
In autumn 2011 he baited for mice across his entire program using the registered control agent zinc phosphide at the recommended one kilogram/ha rate. Some paddocks had to be baited up to five times during the growing season.
After baiting, he monitored crops for 14 days to check for mice activity and crop damage. More zinc phosphide was applied where necessary to reduce the need for resowing.
Mr Wundersitz applauds local industry efforts to secure a temporary emergency permit from the Australian Pesticides and Veterinary Medicines Authority in 2011. He says the temporary permit allowed him to have his own wheat treated with zinc phosphide at bait stations for $1 to $2/kg.
“At $7 to $10/kg, it is not affordable to apply enough bait,” he says. “Having ongoing access to lower-cost baits would allow us to control mice before the numbers build.”
Mr Wundersitz estimates mouse activity in spring 2011 was 10 times that of the previous year, leading to some of the worst damage he has seen and in areas he did not expect.
He says some areas of some paddocks looked like he had used a blunt slasher on the crop.
In spring 2011, he hired an aeroplane to apply bait across half his 5600ha cropping program.
Given the ongoing mouse activity on his farm, Mr Wundersitz is concerned about the efficacy of zinc phosphide bait, especially for spring mouse control, given the high number of mice that carried over into his 2012 crops.
“All we seem to be doing is keeping mice at a level that can sustain life,” he says. “I know of a few grower tests where they found one mouse could eat seven or eight baits before dying.”
His concerns were backed by another study, which showed that while one or two grains of bait was enough to kill a mouse, a controlled feeding study showed a mouse could eat up to 22 grains before succumbing.
Mr Hastings says paddocks at high risk of mouse damage this spring include those with self-sown crops or weeds, which have been subjected to little or no grazing and that carry an abundance of grain or residue on the ground.
“In areas where activity is noted and where the risk factors are high, growers should not hesitate to bait,” he says. “Carry-over populations of mice from autumn may cause severe crop damage at flowering and seed-set, so monitoring for damage and baiting where necessary is imperative.”
Several zinc phosphide bait products are registered for in-crop use. These baits are Schedule 7 poisons and only available to people authorised or licensed under the relevant state or territory poisons control agency.
During spring and summer, Mr Hastings encourages growers to clean up grain spills, control weeds and volunteers, set headers to minimise grain losses and harvest crops before they are overripe to avoid pod shatter or grain losses.
Greg Mutze, of Biosecurity SA, adds that growers using sheep to clean up grain losses after harvest need to graze paddocks hard and early to remove grain before mice have an opportunity to eat it.
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For details on how to monitor mice activity visit www.grdc.com.au/GRDC-FS-MouseControl
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